Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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497 FXUS66 KPDT 141541 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 841 AM PDT Fri Jun 14 2024 .MORNING UPDATE...Taking a look at the Kittitas Valley, we`ve had a wind gust just under 50 mph as recent as just before 8 AM. Therefore will allow the wind advisory to continue until it`s expiration at 11 AM. Otherwise many of our lows ran a bit warm (3-5 degrees or so) compared to forecast expectations, so have made some changes to these temperatures to account for this. Otherwise the morning forecast package remains largely on track. Goatley/87 && .PREV DISCUSSION... /issued 426 AM PDT Fri Jun 14 2024/ SHORT TERM...Today through Sunday...A cooling trend is in store the next several days--nothing dramatic--but temperatures will fall to near to below seasonal averages today and Saturday and about 10 degrees below average on Sunday. Saturday night will be a particularly chilly night as radiational cooling allows overnight temperatures to fall into the mid 20s to mid 30s over the mountains and mid 30s to mid 40s in the lower elevations. It will be mostly dry today, and precipitation will develop from the Cascades westward tonight then increase over the eastern mountains on Saturday. Drier conditions are forecast to return on Sunday. The main weather concern for the short term period will be the gusty winds. A Wind Advisory is in effect for the Kittitas Valley through 11 AM this morning. Although no additional wind highlights are expected, gusty winds will always pose problem for fire spread in dry grassy areas this time of the year. Overall confidence in the short term is high, although there is some uncertainty with just how cool we will get on Sunday. The PacNW will be under a large low pressure trough and cyclonic flow aloft for the next several days. Westerly winds aloft and at the surface have increased, and breezy winds gusting to 25-30 mph have been observed. Ellensburg has observed gusts between 53-57 mph. There are no plans to upgrade the Kittitas Valley to a warning as pressure gradients along the WA Cascades are weakening. The difference between SMP-ELN was 7 mb and now 4.4 mb. Models, including the HREF, show winds gradually decreasing during the day and the NBM probability of gusts greater than 48 kts in the Kittitas Valley is only 20%. Gradients relax tonight but tight enough to maintain breezy winds. Clouds will increase tonight ahead of a shortwave trough, and the trough will bring a 60-80% chance of rain (snow above 4500-5000 feet) along the Cascades and a 30-40% chance of rain (snow above 6000 feet) over the northeast mountains on Saturday. The fairly strong westerly flow aloft will provide rain shadowing off the Cascades so that any precipitation that falls in the Columbia Basin and the Columbia Deschutes Plateau (10-20% chance) will be minimal. Skies will clear Saturday night and winds will diminish, resulting in a chilly night. The probability of freezing temperatures in the lower elevations is low but frost is likely in the Grande Ronde Valley, John Day Basin, and near Bend/Redmond where confidence is 60-80% that temperatures will fall into the mid 30s. Although all the models advertise the trough over the PacNW on Sunday for unseasonably cool conditions, the amplitude of the trough as well as the position of the polar jet are different. Since the majority of the ensembles keep our forecast area on the north side of the jet, the thoughts remain that Sunday will be around 10 degrees below seasonal average. Wister/85 LONG TERM...Monday through Friday...There continues to be some uncertainty in the forecast for Monday into Tuesday with big differences between the very wet deterministic GFS and dry ECMWF. This is due to a much deeper closed low in the GFS compared to a more open wave in the ECMWF. The ensemble clusters favor a more open wave solution. Also looking at the raw ensemble data it appears that a drier scenario is more likely to occur (70% confidence) though there will still be some rain over the eastern mountains and foothills Monday into Tuesday. Stuck with the NBM POPS for this forecast which are close to what you would expect based upon the the ensembles but they could still be a little on the low side (30-55% POPS). The 30 GFS ensemble members are much drier overall tonight compared to last night which suggests that the operational GFS is an outlier and not likely to happen (5-10% chance of 1.0 inch QPF in the foothills and around 2.0 inches in the Northern Blues). Utilized WPC QPF for this forecast which renders .2-.3 inches QPF for the foothills and and .5-.6 inches QPF for the Blues and Wallowas. This is close to what the wetter clusters are showing. On Monday afternoon and evening it is forecast to be breezy to locally windy in the Cascade gaps with the NBM 24 hour probabilities of wind gusts exceeding 40 mph at 30-50% in the typically windy spots under westerly flow regimes. On Monday and Tuesday afternoon the NBM probabilities of TSTMS exceeded 15% (slight chance) for portions of the eastern mountains but very difficult to find much CAPE in the GFS planar fields or forecast soundings. Thus have opted to keep TSTMS out of the forecast for now. It will be quite cool on Monday with high temperatures around 15 degrees below normal. Although there are some differences among the ensemble clusters for the rest of the week, for the most part they all suggest deamplifying flow and decreasing chances for showers. This will result in a warming trend. By Wednesday high temperatures will be about normal for this time of year with slightly above normal temperatures expected for Thursday and Friday. 78 AVIATION...12Z TAFs...VFR conditions will prevail through the forecast period. SCT-BKN clouds at 15-25 kft are expected. Winds will be mostly 15G25 kt for today into the early evening with a slow drop off after 04-06Z. 78 && .PRELIMINARY POINT TEMPS/POPS... PDT 74 49 66 40 / 0 10 10 0 ALW 77 52 69 44 / 0 10 20 0 PSC 80 55 72 45 / 0 0 10 0 YKM 77 46 69 38 / 0 0 10 0 HRI 79 52 71 44 / 0 0 10 0 ELN 72 46 64 40 / 0 0 10 0 RDM 72 41 61 34 / 0 0 0 0 LGD 72 46 61 36 / 0 10 20 0 GCD 75 43 64 36 / 0 0 10 0 DLS 73 52 66 46 / 0 10 20 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...Wind Advisory until 11 AM PDT this morning for WAZ026. && $$ MORNING UPDATE...87 SHORT TERM...85 LONG TERM....78 AVIATION...78